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- Fulati, Alimujiang, et al.
(författare)
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Miniaturized pH Sensors Based on Zinc Oxide Nanotubes/Nanorods
- 2009
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Ingår i: SENSORS. - : MDPI AG. - 1424-8220. ; 9:11, s. 8911-8923
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Tidskriftsartikel (refereegranskat)abstract
- ZnO nanotubes and nanorods grown on gold thin film were used to create pH sensor devices. The developed ZnO nanotube and nanorod pH sensors display good reproducibility, repeatability and long-term stability and exhibit a pH-dependent electrochemical potential difference versus an Ag/AgCl reference electrode over a large dynamic pH range. We found the ZnO nanotubes provide sensitivity as high as twice that of the ZnO nanorods, which can be ascribed to the fact that small dimensional ZnO nanotubes have a higher level of surface and subsurface oxygen vacancies and provide a larger effective surface area with higher surface-to-volume ratio as compared to ZnO nanorods, thus affording the ZnO nanotube pH sensor a higher sensitivity. Experimental results indicate ZnO nanotubes can be used in pH sensor applications with improved performance. Moreover, the ZnO nanotube arrays may find potential application as a novel material for measurements of intracellular biochemical species within single living cells.
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- Riaz, M, et al.
(författare)
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Buckling and elastic stability of vertical ZnO nanotubes and nanorods
- 2009
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 106:3, s. 034309-
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Tidskriftsartikel (refereegranskat)abstract
- Buckling and elastic stability study of vertical well aligned ZnO nanorods grown on Si substrate and ZnO nanotubes etched from the same nanorods was done quantitatively by nanoindentation technique. The critical load, modulus of elasticity, and flexibility of the ZnO nanorods and nanotubes were observed and we compared these properties for the two nanostructures. It was observed that critical load of nanorods (2890 mu N) was approximately five times larger than the critical load of the nanotubes (687 mu N). It was also observed that ZnO nanotubes were approximately five times more flexible (0.32 nm/mu N) than the nanorods (0.064 nm/mu N). We also calculated the buckling energies of the ZnO nanotubes and nanorods from the force displacement curves. The ratio of the buckling energies was also close to unity due to the increase/decrease of five times for one parameter (critical load) and increase/decrease of five times for the other parameter (displacement) of the two samples. We calculated critical load, critical stress, strain, and Young modulus of elasticity of single ZnO nanorod and nanotube. The high flexibility of the nanotubes and high elasticity of the ZnO nanorods can be used to enhance the efficiency of piezoelectric nanodevices. We used the Euler buckling model and shell cylindrical model for the analysis of the mechanical properties of ZnO nanotubes and nanorods.
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- Riaz, M., et al.
(författare)
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Buckling and mechanical instability of ZnO nanorods grown on different substrates under uniaxial compression
- 2008
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 19:41
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Tidskriftsartikel (refereegranskat)abstract
- Mechanical instability and buckling characterization of vertically aligned single-crystal ZnO nanorods grown on different substrates including Si, SiC and sapphire (a-Al2O3) was done quantitatively by the nanoindentation technique. The nanorods were grown on these substrates by the vapor-liquid-solid (VLS) method. The critical load for the ZnO nanorods grown on the Si, SiC and Al2O3 substrates was found to be 188, 205 and 130 µN, respectively. These observed critical loads were for nanorods with 280 nm diameters and 900 nm length using Si as a substrate, while the corresponding values were 330 nm, 3300 nm, and 780 nm, 3000 nm in the case of SiC and Al2O3 substrates, respectively. The corresponding buckling energies calculated from the force displacement curves were 8.46 × 10-12, 1.158 × 10-11 and 1.092 × 10-11 J, respectively. Based on the Euler model for long nanorods and the J B Johnson model (which is an extension of the Euler model) for intermediate nanorods, the modulus of elasticity of a single rod was calculated for each sample. Finally, the critical buckling stress and strain were also calculated for all samples. We found that the buckling characteristic is strongly dependent on the quality, lattice mismatch and adhesion of the nanorods with the substrate. © IOP Publishing Ltd.
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